In the uplink transmission of a cellular system, a baseband transmitting signal of a user equipment (UE) is loaded onto a radio frequency (RF) signal and transmitted through a power amplifier. The transmitted signal with a high peak-to-average power ratio (PAPR) would result in undergoing non-linear distortion of the power amplifier. In the case of the high PAPR, an increase in input back-off of the power amplifier is necessary to prevent the nonlinear distortion of the transmitted signal.
In Long Term Evolution (LTE) of the 3rd Generation Partnership Project (3GPP) (3GPP-LTE), the cubic metric (CM) is used to properly predict a power handling capability of the power amplifier (for example, Non-patent document [1]). For an uplink, single-carrier frequency division multiple access (SC-FDMA) is adopted as the uplink access scheme due to a low CM. In the LTE, the uplink power control is carried out, by using Math.1 (for example, Non-patent document [2]).PPUSCH(i)=min{Pmax,10 log10(MPUSCH(i))+PO—PUSCH(j)+α·PL+ΔTF(TF(i))+f(i)}  [Math.1]Here, each parameter is described follows.                PPUSCH (i) is the transmit power in dBm of the physical uplink shared channel (PUSCH) transmission in sub-frame.        PMAX is the maximum allowed power that depends on the UE power class.        MPUSCH (i) is the size of the PUSCH resource assignment expressed in the number of resource blocks valid for sub-frame i.        PO PUSCH (j) is a parameter composed of the sum of a 8-bit cell specific nominal component PO—NOMAL—PUSCCH (j) signalled from higher layers for j=0 and 1 in the range of [−126, 24] dBm with 1 dB resolution, and a 4-bit UE specific component PO—UE—PUSCH(j) configured by RRC for j=0 and 1 in the range of [−8, 7] dB with 1 dB resolution. For PUSCH (re)transmissions corresponding to a configured scheduling grant, then j=0, and for PUSCH (re)transmissions corresponding to a received PDCCH with a DCI format 0 associated with a new packet transmission, then j=1. αε{0, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1} is a 3-bit cell specific parameter provided by higher layers.        PL is the downlink pathloss estimate calculated in the UE.        ΔTF(TF(i))=10 log10(2MPR(i)KS−1) for KS=1.25 and 0 for KS=0 where KS is a cell specific parameter given by RRC.        f(i) denotes the current PUSCH power control adjustment state in sub-frame i.        
SC-FDMA has a low CM since it allows only continuous resource allocation. The continuous resource allocation is not flexible to achieve multiuser diversity, especially for wideband communications. In DFT-spread-OFDM with discontinuous resource allocation (multi-carrier FDMA) (Non-patent document [3]), the discontinuous resource allocation is employed to achieve the multiuser diversity. The CM of DFT-S-OFDM increases gradually as the number of discontinuous spectrums is getting larger (Non-patent document 4). The CM of DFT-S-OFDM is dependent on the number of discontinuous spectrums.
On the other hand, Orthogonal Frequency Division Multiplexing (OFDM) scheme also allows the discontinuous resource allocation, but has a high CM. The adaptive access scheme of SC-FDMA and OFDM (Non-patent document [2]) employs OFDM to make use of multiuser diversity for high-geometry UEs and uses SC-FDMA to maintain the low CM for low-geometry UEs. A suitable access scheme is selected for the UE according to channel conditions. When the UE changes the access scheme from SC-FDMA to OFDM, the CM increases; while when the access scheme from OFDM to SC-FDMA is made, the CM reduces.    Non Patent Citation 1: 3GPP, R1-060023, Motorola “Cubic Metric in 3GPP-LTE,” January 2006.    Non Patent Citation 2: 3GPP, TS 36.213.820    Non Patent Citation 3: 3GPP RAN1 R1-081752, “Proposals on PHY related aspects in LTE Advanced”, NEC.